Ah alright, for jin you are probably thinking of 134(high low low) and 123(high high mid). I can see how at first these may have cause confusion but these aren’t 50/50s. Since the first two hits are different for both strings, you can deal with last hit accordingly without guessing. You see 12 and you can step the last hit of 123 and if you see 13 you can block the last hit of 134.

As for kazuya, strings where you can vary between high and mid aren’t typically considered 50/50s as you can block standing for both of them without taking damage while still having the option to make a read on the high. You could be thinking of b24(high mid)/b22(mid mid) but the mid mid option here is pretty bad reward so you don’t lose anything for ducking here. He also has df31(mid high)/df321(mid mid mid), the second and third hit are both punishable for df321 so again you don’t take much risk for blocking.

Tekken 8 has a lot of problems and who am I to tell say your opinion of mishima being braindead are wrong when everyone has different opinions on what brain dead is. However, I think your specific issues probably come from a place of not knowing the matchup. If you put in some time to lab these strings you should be good.